We propose to isolate, map and characterize ribosomal regulatory mutants in B. subtilis. By the study, genetic and physiological, of such mutants, we hope to provide some insight into the regulation of ribosome synthesis. The techniques to be employed in selecting such mutants in ribosome regulation will be: nutritional downshifts, uridine suicide, autoradiography, density changes. We will utilize transformation and transduction to map new mutants. Our laboratory has mapped the genes for ribosomal RNA and various mutations in genes for ribosomal proteins. Based upon this work, and that of other workers in the field, a region of the chromosome, the purA - purB segment, is defined which contains most of the information for the synthesis of ribosomes. The gene for bryamycin resistance, from our observation, seems to be close to the DNA sequences coding for rRNA. By mutagenizing bry DNA in vitro we hope to isolate ribosomal RNA regulatory mutants linked to bry, by transformation. In addition, by using a rRNA column technique devised in this laboratory we plan to isolate rDNA, to mutagenize it and to isolate regulatory mutants linked to rRNA genes. We also hope to test these regulatory mutants with an in vitro system for studying ribosome biosynthesis.